The micro-LED technology refers to the LED array of small size integrated on a substrate with high density. As the development of micro-LED technology, it is expected in the industry that a high-quality micro-LED product would come into the market. High quality micro-LED will have a deep impact on the conventional display products such as LCD/OLED that have already been in the market.
In the process of manufacturing micro-LEDs, a micro-LED array is first formed on a carrier substrate. The carrier substrate can be a growth substrate or an intermediate substrate. Then, the micro-LED array is transferred to a receiving substrate of a display device. The receiving substrate can be a display screen or display panel, etc. The display device can be used in an electronic apparatus, such as a micro-display in an argument reality device or a virtual reality device, a watch, a mobile phone a television and so on.
FIG. 1 shows that micro-LEDs 106 on a carrier substrate 103 are being transferred to a receiving substrate 101. The carrier substrate 103 may be a sapphire substrate, for example. A thin film transistor (TFT) layer 102 is formed on the receiving substrate 101. Electrodes 104 are formed on top of the TFT layer 102. The micro-LEDs 106 include epitaxy layers 107 and metal electrodes 108.
Generally, the metal electrodes 108 are P-metal electrodes, and the electrodes 104 are anodes. Alternatively, the metal electrodes 108 are N-metal electrodes and the electrodes 104 are cathodes. Alternatively, the micro-LEDs 106 have a flip structure. In this situation, the metal electrodes 108 may include both P-metal electrodes and N-metal electrodes, and the electrodes 104 may include both anodes and cathodes.
The receiving substrate 101 and the carrier substrate 103 are bonded via a patterned bonding layer (solder) 105, such as solder bumps, resists, pastes, adhesives or polymers, and so on. Specifically, the metal electrodes 108 are bonded with the electrodes 104 via the bonding layer 105.
Laser lifting-off technology can be used in the transfer of micro-LEDs. After the micro-LEDs 106 are bonded with the receiving substrate 101, they can be lifted off by irradiating a laser from the carrier substrate side.
However, the bonding between the metal electrodes 108 and the electrodes 104 is weak. When the micro-LEDs 106 are lifted off from the carrier substrate 103 by using a laser lifting-off, the bonding may be broken and thus the yield loss may be high.
Therefore, there is a demand in the art that a new solution for transferring micro-LEDs shall be proposed to address at least one of the problems in the prior art.